The present invention relates to a process for the formation of composite films and, in particular, to a process for the formation of anisotropic electroconductive sheet materials for mechanically joining and electrically connecting electronic circuit components.
Anisotropic adhesive films are well known and have been used commercially in the electronics industry for some years. Anisotropic adhesive films generally comprise a sheet-like, dielectric, adhesive carrier material which is loaded with conductive particles. The particle loading is kept low so that the formation of electroconductive paths in the X- and Y-axis direction of the adhesive carrier material is avoided. The film is rendered conductive via the particles only in the Z-axis direction of the material.
Anisotropic adhesive films may be used in a variety of applications, such as the bonding of circuits and the bonding of components such as liquid crystals displays and surface mount devices. The most common anisotropic adhesive films are random in nature, i.e. the conductive particles are randomly distributed throughout the adhesive carrier material. The electrical interconnections are influenced by the number of point contacts per unit area and a high contact resistance and low current carrying capability can result.